Malaria, a disease caused by the human protozoan parasite Plasmodium falciparum, affects 300-500 million people annually and is the cause of approximately 2 million deaths per year. The majority of disease pathology is associated with the 48 hour blood stage life cycle of the parasite. During this phase of infection, the parasite uses a highly regulated program of gene expression to orchestrate transition through several morphologically distinct phases. Currently, very little is known about the mechanisms used to achieve this high level of transcriptional control. Due to the absence of canonical eukaryotic transcription factors in P. falciparum, it is likely that post-translational modifications play important and unique roles in the regulation of the parasite life cycle. Small ubiquitin-related modifier (SUMO) is a protein that is used as a posttranslational modifier to alter the function of target proteins. SUMOylation is believed to regulate transcription, protein localization, protein- protein interactions, and the cell cycle. SUMO was recently identified in P. falciparum. Yet it remains difficult to dissect SUMOylation pathways because of the constant removal of SUMO from substrates and the essential nature of the SUMO-specific proteases (SENPs) that carry out this processing event. Thus, new tools that can be used to block the activity of the SENPs with a high degree of temporal control would be highly valuable for the study of SUMOylation in P. falciparum. This proposal outlines our plan to develop small molecule tools to perturb the function of the SENPs in P. falciparum. We hypothesize that SUMOylation is used as a critical regulatory mechanism by the parasite to control key processes necessary for survival inside the host. Therefore, inhibitors of these proteases will allow us to both validate SENPs as potential anti-malarial drug targets and also to isolate populations of SUMO modified proteins by proteomic methods. This data will provide information about how the parasite uses SUMOylation as a general regulatory mechanism. Ultimately, these reagents will help us to gain insight into the functional significance of SUMOylation and may lead to the identification of additional pathways that can be disrupted for therapeutic gain. PUBLIC HEALTH RELEVANCE: We hypothesize that SUMOylation is used as a critical regulatory mechanism by the obligate intracellular parasite Plasmodium falciparum to control key processes necessary for survival inside the host this project outlines plans to develop small molecule inhibitors of the proteases that regulate SUMO removal from substrate proteins. These compounds can be used to dissect the functional role of SUMOylation in the parasite life cycle. Ultimately this information may lead to new therapeutic strategies to treat malaria.